A rack is used to move multiple planar workpieces. The rack is typically provided with a plurality of partition members such that a workpiece is stored between the partition members mounted adjacent to each other. When picking up the workpiece one by one by clamping to hold in a chuck, the pitch between adjacent or neighboring workpieces should be increased in order to insert the chuck between adjacent workpieces. Expansion of the pitch of the workpiece is accomplished by expanding the pitch of the partition members of the rack.
In Japanese Patent Application Publication No. 7-183357, a substrate array pitch conversion device is proposed with a plurality of entry members which may enter into between adjacent substrate holding members (corresponding to the partition members), entry member actuating means to allow or cause the plurality of entry members to enter into and retract from between the substrate holding members, and moving means to move the multiple substrate holding members in a close proximity to each other. The plurality of entry members are arranged such that they enter spaces between neighboring substrate holding members substantially simultaneously (hereinafter referred to as the first conventional technology).
Japanese Patent Application Publication No. 7-183357 also proposes another substrate array pitch conversion device in which, by varying the respective heights of the entry members, after the one entry member has entered between the neighboring substrate holding members, another member adjacent to that entry member is about to enter between the adjacent substrate holding members (hereinafter referred to the second conventional technology).